I had a '98 FXD Super Glide. Got it with 1800 miles on it. I put probably 30k on it and before and after I changed the carb out to an S&S, I would average 45 mpg. The stock carb had the stock needles in it if I remember right. The only reason I have this '97 FLSTC now, is because I got T-boned 2 years ago and this was easy to find and a good price and good mileage on it. I took *everything* off the '98 FXD except the motor and put it on the Heritage - bulbs, ad nausea.

You definitely need to go back to the stock needles on that carb. My Heritage has a 4.2 gallon tank and I *always* fill it before I get to 180 miles, just for ***** sake. I've ridden it 172 miles on one tank once and I've yet to have had to switch to reserve on this bike...and these have no gas gauge!

 

I did another compression test on a fairly warm bike the readings in both were 110 with a little oil added in the cylinders it jumped to 120 in both.

 

Time to do a leak down test..

 

When taking compression test should the bike be warm or cold. I was thinking of upgrading my ignition coil from my stock one to see if that would help with the dry black sooty plugs. I was surprised to see how expensive some of the high voltage coils are. Any suggestions for a upgraded coil under 100 bucks. I have been using Diamondfire powersports e3 spark plugs. My next move would be to replace the entire carb and try a different one. The bike does not run that poorly right now but as the plugs get more full of soot only 100 miles on them right now but starting to get some backfire on deceleration which i did not have when i put the new plugs in.

 

You have not shared any other mods to your bike, air cleaner, exhaust.
Last time mentioning it and I'm out. You have 2 conversation threads about this. On both conversations you have been advised to redo the jet on your carb, it appears that you are not interested in doing that. IDK what to tell you then. You are burning through 2x as much fuel as you should be, good luck.

 

I had a problem with my carb overflowing gas a few years ago. I took my carb to a mechanic he replaced the float needle and changed the the jet from a 46 to a 48. My recent problem I took the carb to another mechanic he went through the carb and found nothing wrong and changed the jet from a 185 to 180 . I have asked him numerous times about changing the 48 back to the 46 or 45 and he always says that it will not solve my problem of dry black sooty plugs and poor gas mileage. That is why I keep looking for other areas that might be causing this problem. I thought maybe the low compression meant that the valves were not seating right and causing the black plugs but not really sure if that is it. That is why I am trying to see if a upgraded coil might help.

 

What air cleaner and exhaust do you have? Have you tested your coil pack? I would still strongly recommend taking your carb back to stock needle and jet to see what happens and then go from there.

 

I have a Arlene Ness air cleaner and kerker 2 in to 1 exhaust. I have not tested the coil yet. was told a coil could test good but when hot may not be work properly. I was told to buy a high voltage coil but the one that was recommended was Accel which are pretty pricey considering that I am not sure that is the problem.

 

A stock ignition coil is fine. There's literally millions of Harleys using them with no problems with a weak spark. Beware of others willing to spend your money.

 

Change the slow jet to a 45 on your own. It's not hard. The 48 is too "fat".